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Pathogenic biallelic variants in POL3RA have been associated with different disorders characterized by progressive neurological deterioration. These include the 4H leukodystrophy syndrome (hypomyelination, hypogonadotropic hypogonadism, and hypodontia) and adolescent-onset progressive spastic ataxia, as well as Wiedemann-Rautenstrauch syndrome (WRS), a recognizable neonatal progeroid syndrome. The phenotypic differences between these disorders are thought to occur mainly due to different functional effects of underlying POLR3A variants. Here we present the detailed clinical course of a 37-year-old woman in whom we identified a homozygous synonymous POLR3A variant c.3336G>A resulting in leaky splicing r.[3336ins192, =, 3243_3336del94]. She presented at birth with intrauterine growth retardation, lipodystrophy, muscular hypotonia, and several WRS-like facial features, albeit without sparse hair and prominent scalp veins. She had no signs of developmental delay or intellectual disability. Over the years, above characteristic facial features, she showed severe postnatal growth retardation, global lipodystrophy, joint contractures, thoracic hypoplasia, scoliosis, anodontia, spastic quadriplegia, bilateral hearing loss, aphonia, hypogonadotropic hypogonadism, and cerebellar peduncles hyperintensities in brain imaging. These manifestations partially overlap the clinical features of the previously reported POLR3A-associated disorders, mostly mimicking the WRS. Thus, our study expands the POLR3A-mediated phenotypic spectrum and suggests existence of a phenotypic continuum underlying biallelic POLR3A variants.

Muscular hypotonia is a feature of Down syndrome (DS), and it affects the tongue and lips. A study on oral dysfunction in children with DS concluded that most of them did not have the tongue strength for completing the oral phase of swallowing. Recognizing the weakness of the oral muscles and improving its motor function positively affects mastication and swallowing, and prevents complications. This cross-sectional study aimed to measure the lip and tongue strength and endurance of children with DS and their typical peers, and compare these two groups with each other using Iowa Oral Performance Instrument (IOPI). Eight children with DS and 33 typical children aged 8–13 years were enrolled in this study. To examine the effect of age on the tongue strength and endurance, we divided the children into three groups of 8–9, 10–11, and 12–13 years old. The results showed that both anterior and posterior tongue strength were significantly lower in children with DS (p = 0.004 and 0.003). But, it was not the case with tongue endurance. Also, in 10–11 years old age group, the mean posterior tongue strength and in 12–13 years old age group the lip endurance was significantly lower in children with DS (p = 0.05 for both). Lips strength and endurance were both remarkably lower in children with DS (p = 0.004 and 0.02). In this study, tongue, and lip strength and endurance in both children with DS and typical ones were measured with IOPI for the first time. Moreover, it provided quantitative data on the strength and endurance of the muscles of the tongue and lips, which can contribute to future studies.

Biallelic pathogenic variants in the neuroblastoma amplified sequence (NBAS) gene were firstly (2015) identified as a cause of fever-triggered recurrent acute liver failure (RALF). Since then, some patients with NBAS deficiency presenting with neurologic features, including a motor delay, intellectual disability, muscular hypotonia and a mild brain atrophy, have been reported. Here, we describe a case of pediatric patient diagnosed with NBAS deficiency due to a homozygous c.2809C > G, p.(Pro937Ala) variant presenting with RALF with severe hyperammonemia, acquired microcephaly and progressive brain atrophy. Not reported in the literature findings include severe hyperammonemia during ALF episode, and neurologic features in the form of acquired progressive microcephaly with brain atrophy. The latter raises the hypothesis about a primary neurologic phenotype in NBAS deficiency.

Based on a patient encounter in which genetically confirmed Marfan's syndrome (MFS) underlay a spontaneously resolving subdural hygroma (SDHy) diagnosed in infancy, we review the literature of MFS clinically manifest in early life (early-onset MFS [EOMFS]) and of differential diagnoses of SDHy and subdural hemorrhage (SDHe) at this age. We found that rare instances of SDHy in the infant are associated with EOMFS. The most likely triggers are minimal trauma in daily life or spontaneous intracranial hypotension. The differential diagnosis of etiologies of SDHy include abusive and nonabusive head trauma, followed by perinatal events and infections. Incidental SDHy and benign enlargement of the subarachnoid spaces must further be kept in mind. SDHy exceptionally also may accompany orphan diseases. Thus, in the infant, EOMFS should be considered as a cause of SDHe and/or SDHy. Even in the absence of congestive heart failure, the combination of respiratory distress syndrome, muscular hypotonia, and joint hyperflexibility signals EOMFS. If EOMFS is suspected, monitoring is indicated for development of SDHe and SDHy with or without macrocephaly. Close follow-up is mandatory.

A clinical case of a boy aged 20 months old with early infantile epileptic encephalopathy (EIEE) type 54 due to mutated HNRNPU gene presumably suffering from genetic generalized epilepsy and impaired psychomotor development is described. Exome-wide sequencing was carried out by using NextSeq 500 (Illumina, USA). Video electroencephalographic (VEEG) monitoring was conducted by using NeuroScope NS425 (Biola, Russia). The patient was noted to suffer from neonatal delayed motor development and muscular hypotonia with atypical petit mal epilepsy with regional onset at the occipital-parietal-posterior temporal areas based on VEEG data developed at age of eight months as well as progressive psychoemotional disorders. Ethosuximide and valproic acid administered together were efficient in alleviating EIEE seizures that requires to be further followed up. The data obtained allow to identify a precise etiology of epilepsy and apply a differential approach to administer anti-epileptic agents.

Thousand and one amino‐acid kinase 1 (TAOK1) is a MAP3K protein kinase, regulating different mitogen‐activated protein kinase pathways, thereby modulating a multitude of processes in the cell. Given the recent finding of TAOK1 involvement in neurodevelopmental disorders (NDDs), we investigated the role of TAOK1 in neuronal function and collected a cohort of 23 individuals with mostly de novo variants in TAOK1 to further define the associated NDD. Here, we provide evidence for an important role for TAOK1 in neuronal function, showing that altered TAOK1 expression levels in the embryonic mouse brain affect neural migration in vivo, as well as neuronal maturation in vitro. The molecular spectrum of the identified TAOK1 variants comprises largely truncating and nonsense variants, but also missense variants, for which we provide evidence that they can have a loss of function or dominant‐negative effect on TAOK1, expanding the potential underlying causative mechanisms resulting in NDD. Taken together, our data indicate that TAOK1 activity needs to be properly controlled for normal neuronal function and that TAOK1 dysregulation leads to a neurodevelopmental disorder mainly comprising similar facial features, developmental delay/intellectual disability and/or variable learning or behavioral problems, muscular hypotonia, infant feeding difficulties, and growth problems., In this study we expand the cohort of individuals with a neurodevelopmental disorder, carrying a de novo variant in TAOK1 (a), thereby further defining the neurodevelopmental disorder caused by TAOK1 malfunctioning. Using both in vivo (b) and in vitro (c) functional assays, we provide evidence that increased as well as decreased levels of TAOK1 cause disruption of neuronal development, showing that TAOK1 plays an important role in neuronal function. Additionally, our data suggests that both gain of function as well as loss of function mutations are potentially causative for the TAOK1‐related neurodevelopmental disorder.

Here we report for the first time on the maternal transmission of mild Coffin–Siris syndrome (CSS) caused by a SOX11 missense variant. We present two sisters with intellectual disability and muscular hypotonia born to non-consanguineous parents. Cogan ocular motor apraxia was present in both sisters. Body measurements were in a normal range. The mother and both daughters showed hypoplastic nails of the fifth toes. A missense variant in SOX11 [c.139 G > A; p.(Gly47Ser)] in both sisters and their mother was identified. Since 2014, variants in SOX11 are known to cause mild CSS. Most described patients showed intellectual disability, especially concerning acquired language. All of them had hypoplastic nails of the fifth toes. It is of note, that some of these patients show Cogan ocular motor apraxia. The facial dysmorphic features seem not to be specific. We suggest that the combination of Cogan ocular motor apraxia, hypoplastic nails of fifth toes, and developmental delay give the important diagnostic clue for a variant in the SOX11 gene (OMIM 615866, MR 27).

Purpose: Biallelic variants in LARS1, coding for the cytosolic leucyl-tRNA synthetase, cause infantile liver failure syndrome 1 (ILFS1). Since its description in 2012, there has been no systematic analysis of the clinical spectrum and genetic findings. Methods: Individuals with biallelic variants in LARS1 were included through an international, multicenter collaboration including novel and previously published patients. Clinical variables were analyzed and functional studies were performed in patient-derived fibroblasts. Results: Twenty-five individuals from 15 families were ascertained including 12 novel patients with eight previously unreported variants. The most prominent clinical findings are recurrent elevation of liver transaminases up to liver failure and encephalopathic episodes, both triggered by febrile illness. Magnetic resonance image (MRI) changes during an encephalopathic episode can be consistent with metabolic stroke. Furthermore, growth retardation, microcytic anemia, neurodevelopmental delay, muscular hypotonia, and infection-related seizures are prevalent. Aminoacylation activity is significantly decreased in all patient cells studied upon temperature elevation in vitro. Conclusion: ILFS1 is characterized by recurrent elevation of liver transaminases up to liver failure in conjunction with abnormalities of growth, blood, nervous system, and musculature. Encephalopathic episodes with seizures can occur independently from liver crises and may present with metabolic stroke.

Kabuki syndrome (KS) is characterized by typical facial features and patients are also affected by multiple congenital anomalies, of which congenital heart anomalies (CHAs) are present in 28.0 to 80.0%. In approximately 75.0% of patients, the genetic causes of KS are caused by mutation in the KMT2D gene. Although KS is a well-characterized syndrome, reaching the diagnosis in neonates is still challenging. Namely, newborns usually display mild facial features; therefore the diagnosis is mainly based on congenital malformations. In our case, a newborn was referred for next generation sequencing (NGS) testing due to the prenatally observed CHA. After birth, a ventricular septal defect (VSD), vesicoureteral reflux, muscular hypotonia, cleft palate, mild microcephaly, and some dysmorphic features, were noted. The NGS analysis was performed on the proband’s genomic DNA using the TruSight One Sequencing Panel, which enriches exons of 4813 genes with clinical relevance to the disease. After variant calling, NGS data analysis was predominantly focused on rare variants in genes involved in VSD, microcephaly, and muscular hypotonia; features observed predominantly in our proband. With the aforementioned protocol, we were able to determine the previously unreported de novo frameshift deletion in the KMT2D gene resulting in translation termination. Although our proband is a typical representative of KS, his diagnosis was reached only after NGS analysis. Our proband thus represents the importance of genotypephenotype driven NGS analysis in diagnosis of patients with congenital anomalies.

Pompe disease (PD) is an autosomal recessive lysosomal storage disorder caused by a deficiency of acid α-1,4-glucosidase enzyme (GAA). PD has two forms, namely the infantile-onset and the late-onset form. In untreated cases, infantile-onset form usually leads to cardio-respiratory failure and death in the first year of life. Herein, we report a newborn with infantile-onset PD characterized by muscular hypotonia, respiratory distress, hypertrophic cardiomyopathy, hepatomegaly, elevated serum enzyme levels of aspartate aminotransferase of 117 IU/L (three times the normal value), alanine aminotransferase of 66 IU/L (1.8 times the normal value), lactate dehydrogenase of 558 IU/L (1.2 times the normal value), and creatine kinase >5,000 IU/L (16 times the normal value). Dried blood spot testing was performed and revealed decreased GAA enzymatic activity (0.07 nmol/mL/h, normal 0.93–7.33 nmol/mL/h). GAA gene analysis performed for confirming the diagnosis showed homozygous mutation c.896T >C (p.Leu299Pro). Initiation of enzyme replacement therapy (ERT) (ERT; 20 mg/kg, once every week) at 28 days of age resulted in weaning off from respiratory support within 1 week after treatment, normalization of cardiac abnormalities, and normal neuromotor development in the 16th month of age. Early diagnosis and early treatment with ERT, especially in the neonatal period, is of great importance to improve cardiac function and motor development in infantile-onset PD.

Congenital muscular dystrophy is an extremely heterogeneous group of hereditary neuromuscular diseases that are clinically characterized by muscular hypotonia, progressive muscle weakness, and dystrophic changes in the muscles. Overlapping clinical symptoms and many genes that have to be analyzed to determine the specific form of the disease in the patient make diagnosis difficult. The molecular genetic stage of diagnosis includes many different methods depending on the clinical hypothesis and their application has not lost its relevance even in the era of massive parallel sequencing. In addition to DNA sequence analysis, the analysis of muscle protein expression can also play a significant role in the diagnosis of congenital muscular dystrophy. In the review, we will consider the most important etiological, pathophysiological, clinical and laboratory data of the main forms of congenital muscular dystrophy known today.

Immunodeficiency 10 is an autosomal recessive disorder presenting with iris hypoplasia, muscular hypotonia and nonprogressive myopathy, recurrent bacterial infections, autoimmune hemolytic anemia, hypohidrosis and nail dysplasia caused by the mutation of stromal interaction molecule 1 gene (STIM1). Herein, we present a new case of STIM1 mediated immunodeficiency, carrying a novel frameshift mutation. Our patient presented with nephrotic syndrome, hypotonia, myopathy, recurrent bacterial infections, thrombocytopenia and autoimmune hemolytic anemia. She is now 23 months old and is on steroid, cyclosporine and monthly IVIG. She has had no recent significant infections and is receiving rehabilitation therapy to improve her motor skills. Rare genetic syndromes should be suspected in patients of consanguineous parents, who present with a set of different manifestations. Gathering all the patient's manifestations together and looking them as one disease should be encouraged.

Kleefstra syndrome is a rare autosomal dominant genetic disorder caused by haploinsufficiency of the EHMT1 (Euchromatic Histone MethylTransferase 1). Patients with Kleefstra syndrome have following most common symptoms: moderate or severe intellectual deficiency, absence of speech, significant diffuse muscular hypotonia, micro-brachycephaly, congenital defects of heart, kidneys, genitourinary tract and recognizable dysmorphic features of face. The article presents 2 similar clinical cases of Kleefstra syndrome in combination with epilepsy. Both patients, along with a typical clinical picture of the underlying disease, have serial epileptic spasms with an onset after first year of life, modified hypsarrhythmia with tendency to synchronization on the electroencephalogram, pharmacoresistant epilepsy. This indicates that Kleefstra syndrome can include epilepsy as one of symptoms of the disease.

Ral (Ras-like) GTPases play an important role in the control of cell migration and have been implicated in Ras-mediated tumorigenicity. Recently, variants in RALA were also described as a cause of intellectual disability and developmental delay, indicating the relevance of this pathway to neuropediatric diseases. Here, we report the identification of bi-allelic variants in RALGAPA1 (encoding Ral GTPase activating protein catalytic alpha subunit 1) in four unrelated individuals with profound neurodevelopmental disability, muscular hypotonia, feeding abnormalities, recurrent fever episodes, and infantile spasms . Dysplasia of corpus callosum with focal thinning of the posterior part and characteristic facial features appeared to be unifying findings. RalGAPA1 was absent in the fibroblasts derived from two affected individuals suggesting a loss-of-function effect of the RALGAPA1 variants. Consequently, RalA activity was increased in these cell lines, which is in keeping with the idea that RalGAPA1 deficiency causes a constitutive activation of RalA. Additionally, levels of RalGAPB, a scaffolding subunit of the RalGAP complex, were dramatically reduced, indicating a dysfunctional RalGAP complex. Moreover, RalGAPA1 deficiency clearly increased cell-surface levels of lipid raft components in detached fibroblasts, which might indicate that anchorage-dependence of cell growth signaling is disturbed. Our findings indicate that the dysregulation of the RalA pathway has an important impact on neuronal function and brain development. In light of the partially overlapping phenotype between RALA- and RALGAPA1-associated diseases, it appears likely that dysregulation of the RalA signaling pathway leads to a distinct group of genetic syndromes that we suggest could be named RALopathies.

Alteration of the KPTN gene, responsible for the coding of kaptin (a protein involved in actin cytoskeletal dynamics), causes a syndrome characterized by macrocephaly, neurodevelopmental delay and epileptic seizures. We report the first Brazilian case of KPTN gene variation, previously described in nine subjects from four interlinked families from an Amish community in Ohio, two Estonian siblings and a 9-year-old boy from Kansas City. We report a case of KPTN-related syndrome in a 5-year-old child which presented macrocephaly, muscular hypotonia, and global development delay. The neurological examination revealed below-expected performance in coordination and balance tests, dyspraxia, and hand-mouth synkinesia. Expressive language was characterized by phono-articulatory imprecision, abundance of phonological processes and morphosyntactic immaturity. Neuropsychological assessment revealed intellectual disability with impairment of verbal and executive functions. Exome sequencing was performed. Analysis revealed a homozygous 2-nucleotide duplication c.597_598dup p.(Ser200Ilefs*55) in the KPTN gene, which is predicted to lead to a translational frameshift and formation of a premature stop codon. The phenotypic profile is similar to the cases described in the other families. Presence of macrocephaly and delayed development indicate the possibility of KPTN gene variation. Genetic testing should be carried out at an early stage in order to reach a timely diagnosis.

Background Several inborn errors of metabolism show cutis laxa as a highly recognizable feature. One group of these metabolic cutis laxa conditions is autosomal recessive cutis laxa type 2 caused by defects in v-ATPase components or the mitochondrial proline cycle. Besides cutis laxa, muscular hypotonia and cardiac abnormalities are hallmarks of autosomal recessive cutis laxa type 2D (ARCL2D) due to pathogenic variants in ATP6V1A encoding subunit A of the v-ATPase. Affected individuals and methods Here we report on three affected individuals from two families with ARCL2D in whom we performed whole exome and Sanger sequencing. We performed functional studies in fibroblasts from one individual, summarized all known probands clinical, molecular and biochemical features and compared them, also to other metabolic forms of cutis laxa. Results Molecular studies revealed novel missense and the first nonsense variant strongly affecting ATP6V1A expression. All six ARCL2D affected individuals show equally severe cutis laxa and dysmorphism at birth. While for one no information was available, two died in infancy and three are now adolescents with mild or absent intellectual disability. Muscular weakness, ptosis, contractures, and elevated muscle enzymes indicated a persistent myopathy. In cellular studies a fragmented Golgi compartment and a delayed Brefeldin A-induced retrograde transport was shown in two and glycosylation abnormalities were present in fibroblasts from three individuals. Conclusion This is the second and confirmatory report on pathogenic variants in ATP6V1A as the cause of this extremely rare condition and the first to describe a nonsense allele. Our data highlight the tremendous clinical variability of ATP6V1A related phenotypes even within the same family. (words: 260) This article is protected by copyright. All rights reserved.

Two siblings with an early onset of a neurodegenerative disease were presented with muscular hypotonia, secondary microcephaly, and severe developmental delay. Seizures were refractory to treatment but could be controlled with a ketogenic diet. Over the course of 5 years, whole exome sequencing (WES) was performed twice in both children. The first time the diagnosis was missed. The next one revealed compound heterozygous mutations in the gene coding for the tubulin folding cofactor D. Technical improvements in WES mandated a new investigation after a few years in children where the diagnosis has not been found.

Stromal interaction molecule 1 (STIM1) mediates extracellular Ca2+ entry into the cytosol through a store-operated Ca2+ entry (SOCE) mechanism, which is involved in the physiological functions of various tissues, including skeletal muscle. STIM1 is also associated with skeletal muscle diseases, but its pathological mechanisms have not been well addressed. The present study focused on examining the pathological mechanism(s) of a mutant STIM1 (R429C) that causes human muscular hypotonia. R429C was expressed in mouse primary skeletal myotubes, and the properties of the skeletal myotubes were examined using single-cell Ca2+ imaging of myotubes and transmission electron microscopy (TEM) along with biochemical approaches. R429C did not interfere with the terminal differentiation of myoblasts to myotubes. Unlike wild-type STIM1, there was no further increase of SOCE by R429C. R429C bound to endogenous STIM1 and slowed down the initial rate of SOCE that were mediated by endogenous STIM1. Moreover, R429C increased intracellular Ca2+ movement in response to membrane depolarization by eliminating the attenuation on dihydropyridine receptor-ryanodine receptor (DHPR-RyR1) coupling by endogenous STIM1. The cytosolic Ca2+ level was also increased due to the reduction in SR Ca2+ level. In addition, R429C-expressing myotubes showed abnormalities in mitochondrial shape, a significant decrease in ATP levels, and the higher expression levels of mitochondrial fission-mediating proteins. Therefore, serial defects in SOCE, intracellular Ca2+ movement, and cytosolic Ca2+ level along with mitochondrial abnormalities in shape and ATP level could be a pathological mechanism of R429C for human skeletal muscular hypotonia. This study also suggests a novel clue that STIM1 in skeletal muscle could be related to mitochondria via regulating intra and extracellular Ca2+ movements.

The paper presents the analysis of clinical and laboratory research of one of the rarely chromosomal pathology, which occur in children - Phelan-MacDermid syndrome. The microdeletion of the long arm of chromosome 22 (del(22)(q13)) and the ring chromosome 22 is the main reason of this syndrome. Genetic counselling was conducted in The Center of medical genetic children hospital “OKHMATDYT”. Three children were examined - 1.5, 7.5, and 18 months, with a diagnosis on admission - mental retardation. Genetic (clinical and genealogical, cytogenetic, including molecular cytogenetic (FISH), biochemical and instrumental examination methods were used. The article presents the sample of teamwork, which consists of a clinical and laboratory part of a syndromological diagnosis. Clinical manifestations of the syndrome are not specific. The most frequent of them is muscular hypotonia, (starting from the neonatal period), stato-kinetic and psycho-speech developmental delay and facial dysmorphism. These signs are needs for medical genetic counselling holding and cytogenetic laboratory diagnostic using the FISH-method (determination of the microdeletion of the long arm of chromosome 22, the ARSA locus). In the absence of the syndrome, it is necessary to differential diagnostics with another unbalanced chromosomal pathology (Prader-Willi syndrome, Angelman, Smith-Magenis and velocardiofascial syndrome) and another genetic syndrome (FraX, Smith Lemli Opitz etc.).

Muscular hypotonia is considered as one of the rarest forms of initial onset signs of TBM, in addition to aphasia and hyponatremia, the awareness of those rare onset signs, a well‐conducted diagnostic approach and early treatment can improve the outcome.

Prader-Willi syndrome (PWS) is a genetic disorder characterized by short stature, low lean body mass, muscular hypotonia, mental retardation, behavioral abnormalities, dysmorphic features, and excessive appetite with progressive obesity. It is caused by lack of expression of genes on the paternally inherited chromosome 15q11.2-q13. This genetic disorder has an estimated prevalence that ranges between 1/10,000-1/30,000. Hypothalamic dysfunction is a common finding in PWS and it has been implicated in several manifestations of this syndrome such as hyperphagia, temperature instability, high pain threshold, sleep disordered breathing, and multiple endocrine abnormalities. These include growth hormone deficiency, central adrenal insufficiency, hypogonadism, hypothyroidism, and obesity often complicated by type 2 diabetes. The aim of this manuscript is to overview the current literature on metabolic and endocrine complications of PWS, focusing on human studies and providing insights on the physio pathological mechanisms. A careful management of metabolic and endocrine complications can contribute to improve quality of life, prevent complications, and prolong life expectancy of PW patients.

A description of the clinical and genetic characteristics of the syndrome of congenital contractures of the limbs and face in combination with muscular hypotonia and psychomotor retardation of 2 patients from Russia is presented. As a result of full-exome DNA sequencing, 2 heterozygous missense mutations c 4355T C and c.3541C G were found in the NALCN gene, leading to amino acid substitutions at the functionally important center of the protein molecule. The effect of identified mutations in the NALCN gene on the function of its protein and approaches to the differential diagnosis of congenital contracture syndrome of the extremities and face in combination with muscular hypotonia and psychomotor retardation with monogenic variants of distal arthrogryposis with autosomal dominant type of inheritance are discussed.

Identifying and characterizing novel causes of autosomal recessive intellectual disability based on systematic clinical and genetic evaluation, followed by functional experiments. Clinical examinations, genome-wide positional mapping, and sequencing were followed by quantitative polymerase chain reaction and western blot of the protein SVBP and its interaction partners. We then knocked down the gene in rat primary hippocampal neurons and evaluated the consequences on synapses. We identified a founder, homozygous stop-gain variant in SVBP (c.82C>T; p.[Gln28*]) in four affected individuals from two independent families with intellectual disability, microcephaly, ataxia, and muscular hypotonia. SVBP encodes a small chaperone protein that transports and stabilizes two angiogenesis regulators, VASH1 and VASH2. The altered protein is unstable and nonfunctional since transfected HeLa cells with mutant SVBP did not reveal evidence for immunoreactive SVBP protein fragments and cotransfection with VASH1 showed a severe reduction of VASH1 in medium and cell lysate. Knocking down Svbp in rat primary hippocampal neurons led to a significant decrease in the number of excitatory synapses. SVBP is not only involved in angiogenesis, but also has vital functions in the central nervous system. Biallelic loss-of-function variants in SVBP lead to intellectual disability.